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Comparative Structural and Electrical Studies of V 2 O 3 and V 2—x Ni x O 3 (0 < x < 0.75) Solid Solution
Author(s) -
Rozier Patrick,
Ratuszna Alicja,
Galy Jean
Publication year - 2002
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/1521-3749(200206)628:5<1236::aid-zaac1236>3.0.co;2-c
Subject(s) - monoclinic crystal system , octahedron , crystallography , rietveld refinement , homogeneity (statistics) , atmospheric temperature range , chemistry , materials science , crystal structure , condensed matter physics , physics , thermodynamics , statistics , mathematics
Abstract V 2 O 3 room and low temperature structures have been refined using PXRD and Rietveld procedures. At 15 K, in addition to the umbrella like opening of V—O bonds associated to the typical large V—V distance through the face shared octahedra (V—V fsh ) we have observed three different V—V distances through the edge shared octahedra (V—V edsh ) : 2.985Å, 2.908Å, and 2.847Å. This splitting is a consequence of the rotation of V—V pairs in a plane itself rotated out of the ( ac ) one which appears to be the origin for the well‐known rhombohedral to monoclinic distortion. Ni for V substitutions drive to a V 2—x Ni x O 3 solid solution with a wide homogeneity range (0 < x < 0.75). Structure refinements on selected compositions show that at both room and 15 K temperatures the typical V 2 O 3 corundum type is kept. At 300 K, the main Ni effect is a drastic decrease of the c parameter associated to a flattening of the octahedra but also to an increase of the M—M fsh distance without rotation of the M—M pairs. This explains the absence of the monoclinic transition in the whole homogeneity and temperature ranges and shows clearly that a large M—M fsh distance is not necessarily associated with the monoclinic form. Despite this large distance observed in the whole temperature range, the electric behavior exhibits a conductor to insulator transition. It is explained in terms of semi conduction via an electron hopping process between V 3+ and V 4+ cations which depends on Ni amounts. This last result implies also that a large M—M fsh distance is not associated with an insulating behavior.